The present invention relates to magnetic recording technology and more particularly to a method and system for providing a glue layer and seed layer for the coil of a write head.
Magnetic data is typically stored on a magnetic recording medium, such as a disk, using a conventional write head. The conventional write head may be a separate head, but is typically part of a conventional merged head. FIG. 1A depicts a conventional merged head 10. The conventional merged head 10 typically includes a read head 11 for reading magnetic data and a conventional write head 19. The conventional read head includes a first shield 12, first and second gaps 14 and 18, respectively, and a magnetoresistive sensor 16. The magnetoresistive sensor 16 is typically a giant magnetoresistance sensor, such as a spin valve. The conventional read head 11 also includes a first pole/second shield 20 (xe2x80x9cfirst polexe2x80x9d). Although used in writing, the first pole 20 also acts as a shield for the conventional read head 11.
The conventional write head 19 is typically an inductive head, including the first pole 20 and a second pole 26. The second pole 26 is typically grown on a seed layer 24. The first pole 20 and second pole 26 are separated by a write gap 22. The write head also typically includes one or more conventional coils 30 which are used to carry current. Two conventional coils 30 are depicted in FIG. 1A. When energized by the current driven through the conventional coils 30, the first and second poles 20 and 26 generate a magnetic field in the write gap. When brought into proximity with the disk or other recording media, the magnetic field writes data to the disk.
FIG. 1B depicts the coils 30 and the surrounding part of the conventional write head 19. The conventional coils 30 include two conventional coils, 30-1 and 30-2, having six turns each. The conventional coils 30 are insulated from the first pole 20, the second pole 26, and each other by conventional insulating layers 32, 40, and 42. Each conventional coil 30-1 and 30-2 includes a conventional conductive layer 38 and 48, respectively, that are typically made of copper. Each of the copper layers 38 and 48 is grown on a conventional seed layer 36 and 46, respectively. The conventional seed layers 36 and 46 are also typically made of copper. The conventional seed layers 36 and 46 are grown on conventional glue layers 34 and 44, respectively. The conventional glue layers 34 and 44 promote adhesion between the corresponding conventional coil 30-1 and 30-2 and the insulating layers 32 and 40, respectively. The conventional glue layers 34 and 44 are typically composed of titanium. Thus, the conventional seed layers 36 and 46 and the conventional glue layers 34 and 44 may carry some current driven through the conventional coils 30-1 and 30-2, respectively.
In order to form the conventional coils 30 for the write head 19, photolithography is typically used. FIG. 2 depicts a conventional method 50 for forming one of the conventional coils 30. Although the method 50 can be used for either conventional coil 30-1 or 30-2, FIG. 2 will be explained in the context of providing the first conventional coil 30-1. FIGS. 3A through 3D depict a portion of the conventional write head 19 during formation of the conventional coil 30-1. Referring now to FIGS. 2 and 3A-3D, the conventional glue layer 34 is provided on the conventional insulating layer 32, via step 52. Thus, step 52 typically includes depositing a layer of Ti on the conventional insulating layer 32. The conventional glue layer 34 promotes adhesion to the insulating layer 32. The conventional seed layer 36, which is typically made of Cu, is then provided on the conventional glue layer 34, via step 54. FIG. 3A depicts the conventional insulating layer 32, conventional glue layer 34, and conventional seed layer 36 after step 54 is performed. A resist structure is provided on the conventional seed layer 36, via step 56. FIG. 3B depicts a portion of the conventional write head 19 after the resist structure 37 is provided. The lines in the resist structure 37 cover the portions of the conventional seed layer 36 above which an insulator will be used to separate turns of the conventional coil 30-1. The resist structure 37 thus includes apertures in areas in which the conventional coil 30-1 will be formed. The conventional coil 30-1 is then deposited, via step 58. Step 58 is typically performed by plating the copper layer 38 onto the conventional seed layer 36. The resist structure 37 is then stripped, via step 60. FIG. 3C depicts the conventional coil 30-1 including copper layer 38. The portions of the conventional seed layer 36 and the conventional glue layer 34 between the turns of the conventional copper coil 38 are then wet etched, via step 62. The wet etch ensures that the turns of the conventional coils 30-1 and 30-2 are insulated from each other. FIG. 3D depicts the conventional coil 30-1 after the conventional seed layer 36 and conventional copper layer 34 have been etched.
One of ordinary skill in the art will readily realize that the trend in magnetic recording is toward higher data transfer rates. Reducing the length of the conventional write head 11, especially the length of the poles 20 and 26, can reduce the head inductance. Thus, the flux rise time is decreased and the data transfer rate can be increased. In order to reduce the length of the poles 20 and 26, either the turns of the coils 30 are more densely packed or the ability of the coils to carry increased current is increased. Thus, the pitch of the coils 30 is desired to be decreased and the aspect ratio of the coils 30 is desired to be increased. The aspect ratio is the ratio of the height of a turn of the coils 30 to the width along the length of the poles 20 or 26 of a turn of the coils 30. The pitch is the width of the coil plus the distance between turns of the coils 30. The pitch or aspect ratio is changed because decreasing the total cross-sectional area of the coils 30 (height multiplied by width) results in excessive electrical resistance and, therefore, excessive heating.
Although it would be desirable to more densely pack the turns of the coils 30, use of the conventional seed layers 36 and 46 and the conventional glue layers 34 and 44 limit the ability to reduce the length of the poles 20 and 26. Conventional photolithography results in the resist structure 37 having lines that are separated by a particular width, currently approximately 0.4 xcexcm. Conventional photolithography may be limited in the width provided by reflective effects. For example the swing curve effect and resist notching alter the resist pattern due to light reflected off of layers beneath the resist structure 37. Thus, portions of the copper layers 28 and 48 are separated by a given distance prior to etching of the conventional seed layer 36 or 46 and the conventional glue layer 34 or 44. The wet etch which is used to etch the conventional seed layers 36 and 46 and the conventional glue layers 34 and 44 limits the pitch of the coils 30. The wet etch of step 62 etches not only the conventional seed layer 36 and 46 and conventional glue layers 34 and 44, but also etches the copper layers 38 and 48. The wet etch is also isotropic. Thus, both the height and width of the copper layers 38 and 48 are reduced by the wet etch. This reduction in the height and width of the copper layers 38 and 48 can be seen in FIGS. 3C and 3D. For example, if the seed layer 36 or 46 is approximately 0.1 xcexcm thick, a wet etch which etches through the conventional seed layer 36 or 46 may reduce the height of the copper layer 38 or 48 by 0.1 xcexcm and increase the distance between turns of the coils 30 by 0.2 xcexcm. Given that the distance between the turns for the copper layer 38 or 48 for some photolithographic processes is approximately 0.4 xcexcm prior to the wet etch, the affect of the wet etch on the coils 30 can be significant. Consequently, both the resistance of the coils 30 for a particular resist structure 37 and the distance between turns of the coils 30 are increased. Furthermore, the aspect ratio of the coils 30 is also increased. The ability of the coils 30 fabricated at the desired pitch and aspect ratio to allow for a reduced pole length may be compromised. Thus, the wet etch reduces a manufacturer""s ability to provide a conventional write head 19 having increased data transfer rates.
The wet etch also affects the yield for the conventional coils 30 and, therefore, the conventional head 10. The wet etch step 62 often results in an undercut of the conventional seed layers 36 and 46 and the conventional glue layers 34 and 44. In other words, the width of the copper layer 38 or 48 is larger than the widths of the conventional seed layer 36 or 46 and the conventional glue layer 34 or 44. The undercut occurs because the wet etch is substantially isotropic. Thus, the wet etch not only etches vertically into the conventional seed layers 36 and 46 and the conventional glue layers 34 and 44, but also horizontally along the conventional seed layers 36 and 46 and the conventional glue layers 34 and 44. The undercut is depicted in FIGS. 1B and 3D. Because of the undercut, the conventional copper layer 38 or 48 may move more readily than if the widths of the conventional seed layer 36 or 46 and the conventional glue layer 34 or 44 were approximately the same as for the conventional copper layer 38 or 48. The turns of the conventional coils 30 may move enough to touch each other. Thus, one or more turns of the conventional coils 30 may be shorted. The conventional coils 30 and, therefore, the conventional write head 19 may be unusable. Consequently, the yield of the conventional write head 19 is reduced.
Accordingly, what is needed is a system and method for improving the data transfer rate of a write head. It would also be desirable if the method and system resulted in a higher yield or simplified processing of the head. The present invention addresses such a need.
A method and system for providing a write head is disclosed. The write head includes at least one pole and an insulating layer. The at least one pole is for writing magnetic data. The method and system comprise providing an intermediate layer and providing at least one conductive coil. The intermediate layer is disposed between the insulating layer and the at least one conductive coil. The intermediate layer is composed of at least one material capable of being dry etched. The at least one conductive coil is in proximity to the pole and is for carrying a current to energize the pole during writing.
According to the system and method disclosed herein, the present invention provides a mechanism for providing the coil(s) of the write head. Because the intermediate layer can be dry etched, overetching of the coils and undercutting of layers under the coils is reduced or substantially eliminated. Thus, write heads having higher data transfer rates and higher yields may be provided.